Xanthones in Heterocyclic Synthesis. An Efficient and General Route for the Synthesis of Regioselectively Substituted Phthalazines

Abstract

Xanthone undergoes regioselective substitution and nucleophicallytriggered ring opening to the corresponding ketone.Hydrazone of the latter oxidatively rearranges to ortho-diacylarenes, which, then, with hydrazine gives regioselectively substituted phthalazines.Molecular modeling analysis and 1 H NMR spectra indicate an intramolecular H-bonding engaging phenol OH and phthalazine N-3 atom.